The present invention relates to a process control terminal, and more particularly to a process control terminal having the capability to simultaneously display process control information and other unrelated information in mutually exclusive portions of a display screen.
The field of process control relates to the interactive control of complicated processes such as chemical processes used in chemical and oil refineries, processes used in food processing, processes used in pulp and paper producing plants, etc. The typical variables that need to be controlled during such processes include temperatures, pressures, flow rates, and quantities.
In order to monitor and control such processes, process control networks are typically used. Such a network includes a number of process control terminals connected to a plurality of process controllers which monitor the processes. The process control terminals are monitored closely by operators, who may be required to respond quickly to visual alarm messages on the process control terminal screens. Such alarm messages may indicate dangerous or undesirable conditions, such as a dangerously high pressure or a temperature that is out of range, which could result in damage to the process control facility, such as rupture of a conduit or boiler, or in defective product.
The operator is also be required to respond to attention messages generated on the process control terminal screens. Such an attention message indicates the need for the operator to take a particular action, depending upon the particular message. For example, the supply of a chemical used in a process may be low. In this case, the process controller monitoring the supply of the chemical would transmit an electronic low supply message to the appropriate process control terminal, which would then show the corresponding visual message on the screen. The operator, upon seeing the message, would make sure that the particular chemical supply would be refilled.
When monitoring a process control terminal, an operator typically experiences relatively extended periods of time during which no alarm or attention messages are generated. As a result, the operator has nothing to do. Not only is this lack of duties an inefficient utilization of the operator""s time, but the operator may become bored. One approach to remedying this problem might be to provide the operator with a separate computer and display screen so that the operator could perform additional tasks during his spare time. However, this approach suffers the drawback that another display screen and computer are required, resulting in the need for extra space as well as cost.
One general approach to a similar problem is described in U.S. Pat. No. 4,761,642 to Huntzinger. Huntzinger discloses a computer system which has the capability of simultaneously responding to multiple application programs being executed by a host computer. A single display terminal is connected to the computer system, and a window is shown for each active application program being executed by the host computer. The Huntzinger system has serious disadvantages in the context of process control terminals. One using the Huntzinger system may hide windows from view by xe2x80x9cburyingxe2x80x9d one window behind another window so that portions of the buried window do not appear on the screen. Furthermore, the user may xe2x80x9ccollapsexe2x80x9d a window, which causes the entire window to disappear from the screen, the only remnant of the collapsed window being a small icon displayed along the edge of the screen.
If used in a process control system, the Huntzinger system could have disastrous consequences. If the operator were to partially obscure one or more windows relating to process control, the operator might miss alarm or attention messages, which could result in damage to the process control facility or defective product. Moreover, the application of the Huntzinger system to the process control area would defeat the operator""s primary responsibility, that of monitoring the process.
The present invention overcomes these and other disadvantages by providing a process control terminal which allows an operator to perform both process control functions and application functions which may be unrelated to process control functions. The application functions are performed in connection with a host computer connected to the process control terminal. To prevent application information for display on the screen of the process control terminal from overwriting process control information, including alarm messages, for display on the screen, the process control terminal reserves a first portion of the screen exclusively for process control information and a second portion of the screen exclusively for application information.
In a preferred embodiment, this feature of the invention is accomplished by adding a predetermined vertical pixel offset to the application information received from the host computer for display on screen of the process control terminal. As a result of the offset, the application information is guaranteed not to be displayed in the screen portion reserved for process control information including alarms.
In a preferred method in accordance with the invention, the process control terminal receives process control information from a process controller, determines the existence of an alarm condition, and displays process control information in a first screen portion reserved exclusively for process control information. The process control terminal also receives application information from a host computer and displays the application information in a second screen portion reserved exclusively for application information. As a result, of the mutually exclusive screen portions, application information cannot overwrite process control information and thus cause a process control operator to miss alarm conditions.
In another aspect, the process control terminal of the invention emulates a standard Digital Equipment Corporation (DEC) terminal so that the invention may be used in preexisting computer systems. A process control terminal in accordance with this aspect of the invention responds to various electronic signals the same way a standard DEC terminal would. For example, the process control terminal moves a cursor on the screen up in response to the receipt of the character xe2x80x9cAxe2x80x9d from the host computer; moves the cursor down in response to the receipt of the character xe2x80x9cBxe2x80x9d; erases a portion of a line of text in response to the receipt of the character xe2x80x9cKxe2x80x9d; deletes a portion of a line of text in response to the receipt of the character xe2x80x9cMxe2x80x9d; and draws a curve in response to the receipt of a character string including the character xe2x80x9cC.xe2x80x9d
Another feature of the invention is an automatic login feature that allows an operator to login to a computer program without the need for typing in a username or password. This feature of the invention is accomplished by accessing a predetermined portion of memory in response to an operator login request. If the predetermined portion of memory contains login information, this login information is compared with preselected login information to determine whether access to the computer program should be granted. If the stored login information matches to the preselected login information, the operator is logged in to the computer program automatically without the need for the operator to type a username or password.